The present invention pertains to a hemming apparatus with an outer hemming device and/or an inner hemming device as well as a clamping device with pressing and clamping elements
Such a hemming apparatus has been known from DE-A 43 30 683. It has a hemming bed that can be raised and lowered and two hemming units, each of which has two different hemming tools for prehemming and finishing hemming. The hemming drive is arranged on the hemming bed, which performs the hemming stroke by a lifting movement. The hemming units can be pivoted only onto the hemming bed, and the prehemming and finishing hemming tools are brought into the working position by a vertical adjustment of the hemming bed. The workpiece is clamped on the hemming tools, which grasp the workpiece together and simultaneously, via spring-loaded holding-down devices.
The object of the present invention is to provide a better hemming apparatus.
According to the invention, a hemming apparatus is provided with an outer hemming device and/or an inner hemming device as well as a clamping apparatus with pressing and clamping elements. The clamping apparatus has one or more leading pressing and clamping elements.
The hemming apparatus according to the present invention can operate with different clamping apparatus. The use of leading pressing and clamping elements, which make possible a predeterminable clamping sequence of any freely selectable points of the workpiece or workpieces, is particularly advantageous. These pressing and clamping elements are mounted in such a way that they are deformable or can yield, so that their leading function can be eliminated at the end of the clamping movement so that a simultaneous clamping of the workpiece or workpieces takes place at all intended points.
The hemming apparatus according to the present invention require little design effort and have freely settable and adjustable kinematics. Retooling operations and tool change can be performed rapidly and simply. The hemming unit can be controlled very easily and accurately. The drive is uncomplicated. The entire hemming unit is insensitive to disturbances and also has a high reliability in operation due to the small number of moving parts. This also leads to advantages for simple and inexpensive maintenance.
The basic components of the hemming units are standardized and independent from the shape of the workpiece. They can therefore be manufactured in advance and can be reused in the case of a tool change.
The hemming apparatus according to the present invention makes it possible, in particular, to change the hemming tools independently from the hemming stroke. It is particularly advantageous in this connection that the hemming stroke can be very short and can be carried out with a high force. In particular, the hemming head according to the present invention does not require an additional height and feed height in the hemming area. This is especially true in the case of the preferred design as a rotating roll. If a plurality of hemming units are used, their hemming tools can be changed independently from one another.
The entire hemming unit is compact and can be placed especially favorably and simply on the hemming apparatus as a result. In addition, the small overall height offers advantages concerning the other components. For example, the rotating roll makes possible tool change under the clamping apparatus, which can remain as a result in position at the workpiece and holds same during the tool change. The small overall height makes it possible, in addition, to arrange the hemming unit obliquely in order to thus optionally achieve a better direction of the hemming force at right angles to the surface of the workpiece. If the hemming unit according to the present invention is arranged obliquely on the outside of the workpiece, the present invention has the advantage that the interference distance from a possible inner hemming device is greater because of the small overall height of the hemming unit.
The design of the hemming unit according to the present invention also makes it possible to use hemming tools of any desired shape and size. A longer or multipart hemming head, which is arranged on two or more hemming units and is supported via intermediate supports in a suitable manner, may be optionally used for this purpose.
The hemming head may carry a plurality of hemming tools. In the preferred embodiment, it carries two hemming tools for prehemming and finishing hemming. The design of the hemming head as a rotating roll has the advantage that an especially simple kinematics with reliable guiding and setting is guaranteed for adjusting the tool. In particular, the hemming head can be set and positioned completely independently from the hemming drive, which generates the hemming stroke. The pivoting drive for the hemming head preferably has a crank drive. This makes it possible to make do with weaker driving forces for adjusting the hemming head and to nevertheless generate strong, positive-locking holding forces in the working position in order to thus transmit correspondingly strong hemming forces.
The hemming tools may have one or more centering inserts, which have a stop and centering function for the workpiece or workpieces. These centering stops are also advantageous for holding and positioning the workpiece during tool change and during the turning of the hemming head. Special advantages arise when the hemming apparatus is designed as a combination device with an outer and inner hemming device.
The centering inserts facilitate the staggered feed in time of the hemming unit. The final shape of the workpiece can be influenced as a result. In addition, errors due to warping or dimensional errors can be compensated.
The hemming unit may have one or more movable and driven tensioners or clamps, which can be actuated independently from the hemming tools. It is advantageous in this connection for the clamps to be arranged behind the hemming heads and to extend over them. As a result, the hemming heads can be rotated under the clamps for tool change, while the workpiece or workpieces can remain clamped during a tool change staggered in time. The clamps associated with the hemming unit or hemming units may replace an internal clamping device, e.g., a vertical or pivotable clamping frame. They may alternatively also complement same.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.